Preparation of sulfuryl chlorofluoride



Patented July 31, 1951 PREPARATION OF SULFURYL CHLOROFLUORIDE Harold Gilman McCann, Deer Park, and Horace Quay Trout, Brooklyn, N. Y., assignors to Allied Chemical & Dye Corporation, New York, N. Y., a corporation of New York N Drawing. Application August 31, 1948, Serial No. 47,146

8 Claims. (01. 23-.-14.)

This invention relates to the preparation of ,sulfuryl chlorofluoride, a material suitable for use, e. g. as an intermediate, in other chemical operations.

It has been proposed to make sulfuryl chlorofiuoride (SOzClF) by reacting sulfuryl chloride (SOzClz) with antimony trifiuoride (SbFs) fluorinating agent. The disadvantages of this process are the necessity of providing an additional catalytic material, e. g. antimony pentachloride (SbCls) to promote the reaction between the 802012 and the SbFs, the requirement of employing superatmospheric pressures, such as pressure approximately 100 p. s. i. g., and the fact that the fiuorinating agent, once consumed, cannot be reused, i. e., antimony trichloride (SbCl3) to which the SbFz is converted by reaction with the SO2C12 cannot readily be reconverted to antimony trifluoride for reuse in the process.

It is an object of this invention to provide for the manufacture of good yields of SOzClF by procedures which are not subject to the aforementioned disadvantages. Other objects and advantages will appear hereinafter.

According to our invention, we have found that, when SOzClz is subjected, at certain elevated temperatures, to the action of materials such as cobalt trifluoride (CoFa), silver difluoride (AgFz) or manganese trifluoride (MnFs), or mixtures thereof, these materials function as fiuorinating agents and displace chlorine of the SO2C12 with resultant formation of SOzClF. Further, we find that, at the relatively low elevated temperatures herein stated, the foregoing materials act as fiuorinating agents at substantially atmospheric pressures. An outstanding feature of the invention lies in the discovery of SO2Cl2 fiuorinating agents, 1. e. those above named, which are of such inherent nature as to permit, in conjunction with reaction temperature control, easy regulation of the degree of SOzClz fiuorination. Moreover, we have found fluorinating agents which are of such characteristics and properties that on exhaustion, the spent fluorinating agents may be readily reconstituted, by simple fluorination by elemental fluorine, to their original active compositions. A distinguishing characteristic of the metal components of the herein fluorinating agents is that the oxides of the metalsnamely, cobalt, silver and manganese, catalyze the oxidation of CG to CO2.

Practice of the invention comprises introducing 802012 in vapor form into a reaction chamber containing the solid fiuorinat-ing agent employed and equipped with means to maintain in the reaction zone the herein specified temperatures, withdrawing the resulting gaseous reaction mixture from the reaction zone, and recovering the sought-for end product from such reactionlmix-r ture.

The temperatures at which SO2C12 may be subjected to the action of the chlorine-displacing fiuorinating agents of the invention are preferably those sufliciently elevated to effect formation of a substantial amount of SOzClF. According to the invention, it has been found that control of temperature is a crtical factor in determining the degree of SOzClz fluorination, and also the yield of SO2C1F product. In practice of the invention generally, the reaction zone should be maintained at temperatures in the range of 110 C. to 220 C. We find that at temperatures below about to C. no significant yield of SOzClF is obtained. The SOzClF manufacture objective of the invention arises out of the discovery that under suitable reaction zone temperature regulation, SOzClz may be fluorinated for the most part. to SOzClF as distinguished from SOz-Fz. Acceptable partial fiuorination of SOaClz and reasonable yields of SOzClF' may be obtained by permitting reaction zone temperatures to run as high as 220 C. However, realization of the best advantages of the invention with respect to SOzClF yield results from our discovery that, to this end, partial fluorination of 802012 and optimum yields of SOzClF are obtained when maximum temperatures in the reaction zone are maintained in the range of to C. While not limited to operation at atmospheric pressure, since SOzCl-F may be obtained by use of reduced or superatmospheric pressures, an outstanding advantage of our process is that normal atmospheric pressure may be employed as previously mentioned.

Contacting of 802012 reactant and fluorinating agent may be effected in any suitable manner. For example, when using a single reactor, the reaction zone therein containingthe fluorinating agent may be maintained at the desired reaction temperature as by adequate external heating. SO2C12 vapor may be continuously introduced into and flowed thru the. zone at a rate satisfactory for effecting the desired reaction to form the SOzClF reaction product: which may be continuously withdrawn from the reactor. Flow of feed material over the fiuorinating agent may be intermittent depending upon the particular con-' ditions to which it desired to. adapt the process. When the fluorinating properties of the fluorinating agent become exhausted, the stream of SOzClz may be stopped to permit regeneration of the metallic fluoride as hereinafter described. For continuous operation with one reactor, a countercurrent flow of substantially completely fluorinated metallic fluoride thru the reactor may be utilized with provision for continuous removal and refluorination of the agent. Further, for continuous operation it may be desirable to use two or three reactors arranged in parallel. While reactive metallic fluoride is being utilized in one reactor, the exhausted agent in another reactor may be undergoing refluorination. Since a substantial amount of time may be required to purge a reactor with nitrogen at the start of a cycle to remove fluorine and to sweep out the products at the end of the cycle, it may be advantageous to utilize a third reactor in the system.

The reaction of SO2C12 with the fluorinating agent according to our invention is exothermic. In order to remove more effectively the heat generated by this reaction and thereby facilitate control of temperature in the reaction zone, we prefer to mix inert diluent gas such as nitrogen with vapors of SOzClz introduced into the reaction zone. Such diluent gas also aids in the removal of unreacted SO2C12 from the cooler portions of the reactor exit pipe. The amount of diluent gas employed may be sufficient to provide for smooth temperature control and removal of all vapors from the reactor without unduly complicating the separation of reaction product from the inert gas.

There is no critical maximum time of contact of SO2C12 reactant with chlorine-displacing fluorinating agent, above which appreciable side reactions occur or other adverse effects are obtalned. At long contact times, however, the capacity of the reactor is low, and an economic disadvantage inheres in the operation. On the other hand, if time of contact is too short the reaction of SOzClz to produce the desired product may be incomplete. This results in the appearance of relatively small amounts of SOzClF and relatively large amounts of unreacted 802012 in the reaction product. Such unreacted SO2C12 ma be recovered from the reaction product and returned to the reaction, but in such operation cost of recovering and recycling unreacted SO2CI2 may amount to an appreciable item. Accordingly, the time of contact employed is determined b balancing the economic advantage of high reactor capacity obtained at short contact times against cost of recovery of unreacted SO2C12. Further, flow of gaseous reactants thru the reaction zone is dependent upon variables, such as scale of the operation, quantity of fluorinating agent in the reactor, and specific apparatus employed, and optimum rate of flow for any given conditions may be determined by a test run.

While we do not intend to limit our invention to any theory or mechanism of reaction, we believe that SO2CI2 reacts with our chlorine-displacing fluorinating agents according to the following chemical equations:

It appears that the fluorine of the fiuorinating agent displaces chlorine in SO2C12 to produce SOtzClF. Free chlorine is obtained as a by-produc As heretofore indicated, it is an advantage of our process that the chlorine-displacing fluorinating agent may be regenerated, i. e., restored to its original form and reused in subsequent operations. The metal fluoride, reduced to a fluoride of lower valence by its reaction with the 502C]: as heretofore shown, is restored to its form of higher valency by merely bringing the reduced fluoride into contact with gaseous fluorine at suitable temperature. This regeneration of spent fluorinating agent may be suitably carried out in situ in the reaction zone. Gaseous fluorine is passed over the spent catalyst at a temperature suitable for the regeneration of catalyst, e. g. 250 C., and the flow of fluorine continued until the desired degree of regeneration has been obtained. Fluorine is then swept from the reactor, the temperature readjusted and introduction of SOzCl: resumed.

The product mixture from the reactor, containing SOzClF (B. F. plus 7.1 C.) Clz (B. P. minus 34.6 C.); unreacted SOzClz (B. P. plus 69.1 C.); and some SOzFz (B. P. minus 55 C.) may be condensed and the components separated by low temperature distillation and fractionation. Sought-for SOzClF of relatively high purity may be obtained by this procedure.

The reactor, which may suitably be in the form of a cylindrical tube, is constructed of material resistant to the corrosive attack of gaseous chldrine and fluorine, such as steel. In order to facilitate exposure of solid chlorine-displacing fluorinating agent to SOzClz vapors we prefer to stir or otherwise mechanically agitate the bed of solid material in the reaction zone. Suitable means for agitating the catalyst bed may be inserted into the tube at its ends. Inlet and outlet pipe connections, through which feed material is introduced into, and product withdrawn from the reactor, respectively, are supplied at opposite ends of the reactor tube.

The following examples are illustrative of our invention, the parts being by weight:

Example 1.--A steel reactor, consisting of a horizontal tube 24 inches long and 2% inches I. D. and having inlet and outlet connections at opposite ends, was equipped internally with a /z" shaft supported at either end by suitable bearings and associated packing glands, and carrying paddle blades. Means for heating the unit externally with gas were supplied and five thermocouples were placed 4 inches apart along the bottom of the reactor. The reactor was charged with 600 parts of COFs and the temperature adjusted so that reaction zone temperature at the gas inlet was about -120 C., at the center 150-160 C. and at the exit end about 140 C. A slow stream of nitrogen gas was bubbled through a flask of SOzClz heated just below the boiling point and the SOzClz-Nz mixture was then introduced into the reactor through the inlet connection. In this manner, while rotating the shaft and thereby stirring the bed of CoFz, 398 parts of SOzClz were passed into the reactor in 2 hours and 10 minutes. Nitrogen was passed through the reactor for an additional 10 minutes and the reaction products, which had been collected in a trap cooled in dry-iceacetone mixture, were subjected to fractional distillation. 232 parts of SO2C1F, 72.5 parts of unreacted SOzClz, 84.5 parts of free C12 and 13.0 parts of SO2F2 were obtained. The yield of SOzClF based on SOzClz not recovered was 81.5%.

The temperature of the reactor was then raised to approximately 250 C. and a stream of fluorine gas was passed over the bed while agitating the bed. The shaft bearings were protected from contact with fluorine by suitable streams of nitro gen gas. This treatment was continued for 2 hours after which the introduction of fluorine into the reactor was discontinued and the reactor purged of fluorine by continuing to pass a stream of nitrogen therethrough. Thereafter, the fiuorinating agent thus regenerated was employed for further conversion of 802012 to SOzClF.

Example 2.-Using the procedure and apparatus described in Example 1, 399 parts of SOzCl-z were passed thru the reactor in 50 minutes, during which time the temperature of the reactor in the hottest zone was 170-195 C. The reaction zone exit, after liquefaction, was distilled and there was obtained 120 parts of SO2C1F, some SO2F2, C12 and about 117 parts unreacted SOzClz. The yield of SOzClF based on SO2C12 not recovered was 49%.

Example 3'.--Using the apparatus and general procedure of Example 1, 365 parts of SO2C12 were passed in 2 hours thru the steel tube into which 550 parts of AgFz had been introduced. During this time the temperature in the reactor was maintained at about 1i7-152 C. On distillation of the mixture caught in the dry-ice trap, 117.5 parts of SO2C1F' and 131 parts of SOzCIz were recovered, representing an SOzCIF yield of 57% based on SOzClz not recovered.

Example 4.-In another operation similar to those of the above examples, the reactor was charged with about 500 parts of MnFa. SO2C12 was flowed through the reaction zone, maintained at temperature of 159162 C., for 2 hours and 40 minutes. On distillation of the material caught in the dry-ice trap, 107 parts of SO2CIF were recovered, and yield of the latter was in excess of 40%.

We claim:

1. In the preparation of SOzClF, the step which comprises subjecting SO2C12 to the action of a fluorinating agent of the group consisting of COFs, AgFz and MnFa, at temperature in the range 110 to 220 C. for time sufficient to form an appreciable amount of $020115.

2. The method of preparing SOzClF which comprises subjecting SO2C12 to the action of a fluorinating agent of the group consisting of CoFs, AgFz and MnFa, at temperature in the range 145 to 170 C., for time sufiicient to form a reaction mixture containing an appreciable amount of SO2ClF, and recovering SOzClF from said reaction mixture.

3. The method of preparing SOzClF which comprises subjecting SO2C12 to the action of a fluorinating agent of the group consisting of CoFs, AgFz and MnFa, at substantially atmospheric pressure and at temperature in the range to 220 C., for time suificient to form a reaction mixture containing SO2CIF, and recovering SOzClF from said reaction mixture.

4. The method of preparing SO2C1F which comprises introducing vapors of SOzClz into a zone containing COFs and maintained at temperature in the range 110 C. to 220 C. withdrawing from said zone a reaction mixture comprising SOzClF, and recovering SOzClF from said reaction mixture.

5. The method of preparing SOeClF which comprises introducing vapors of SO2C12 into a zone containing MnFs and maintained at temperature in the range 110 to 220 C., withdrawing from said zone a reaction mixture comprising SOzClF, and recovering SOiClF from said reaction mixture.

6. The method of preparing SOzClF which comprises introducing vapors of SO2C12 into a zone containing AgFz and maintained at temperature in the range 110 to 220 C. withdrawing from said zone a reaction mixture comprising SozClF, and recovering SOzCIF from said reaction mixture.

7. The method of preparing SO2C1F which I comprises introducing vapors of SOzClz into a zone containing COFs and maintained at temperature in the range to C., contacting said vapors with said CoFs for a time sufiicient to convert at least part of said COFs toCoFa to form a reaction mixture comprising a substantial amount of SOzClF, withdrawing said reaction mixture from said zone, and recovering SOzClF from said reaction mixture.

8. The method of preparing SOzClF which comprises introducing vapors of 802012 into a zone containing COFs and maintained at substantially atmospheric pressure and at temperature in the range 145 to 170 C., contacting said vapors with said COF3 in said. zone for a time suflicient to form a reaction mixture comprising a substantial amount of SOzClF, withdrawing said reaction mixture from said zone, and recovering SOzClF from said reaction mixture.

Booth et al.; J. Am. Chem. 800., vol. 58 (1936), pages 63-66.

Ruff et al.; Z. fur Anorg. u Allg. Chem, vol 219 (1934), pages 147-148.

Number 

1. IN THE PREPARATION OF SO2CLF, THE STEP WHICH COMPRISES SUBJECTING SO2CL2 TO THE ACTION OF A FLUORINATING AGENT OF THE GROUP CONSISTING OF COF3, AGF2 AND MNF3, AT TEMPERATURE IN THE RANGE 110* TO 220* C. FOR TIME SUFFICIENT TO FORM AN APPRECIABLE AMOUNT OF SO2CLF. 